Stephanie van Hoppe

110 Chapter 5 increased brain concentration, respectively 2.2-fold (P = 0.008) and 1.9-fold (P = 0.01) relative toWT mice. However, when both ABC transporters were absent, ponatinib brain concentration was increased by a drastic 25.5-fold compared to WT brain (Figure 3A, P < 0.0001). Correcting for differences in plasma concentration, the brain-to-plasma ratio of Abcb1a/1b;Abcg2 -/- mice remained markedly higher compared to wild-type mice, while the single ABC transporter knockouts were also still somewhat higher, albeit not significantly (Figure 3B). Correcting for the plasma AUC, the brain accumulation of ponatinib 24 h after oral intake was again clearly and significantly increased by 24- fold in Abcb1a/1b -/- ;Abcg2 -/- mice, and by 2.2- and 1.9-fold in the single Abcg2 -/- and Abcb1a/1b -/ - mice (Figure 3C). These data indicate that ponatinib is kept out of the brain by both Abcb1a/1b and Abcg2, and that these proteins are able to largely take over each other’s transport function at the BBB. Only when both transporters were absent, ponatinib accumulated very substantially in the brain. At the same time, we observed no substantial impact of Abcg2 and Abcb1a/1b on the liver distribution of ponatinib (Figure 3D-F), illustrating the specific function of these transporters in the BBB. Figure 3. Brain and liver concentration ( A, D ), tissue-to-plasma ratio ( B, E ) and relative tissue accumulation ( C, F ) of ponatinib in female WT, Abcg2 -/- , Abcb1a/1b -/- and Abcg2;Abcb1a/1b -/- mice 24 h after oral administration of 10 mg/kg ponatinib. *, P < 0.05; **, P< 0.01; ***, P < 0.001 compared to WT mice. Data are given as mean ± SD. n = 4-5 mice per group. Liver concentration ( n g/g) Wild-type Abcg2-/- Abcb1a/1b-/- Abcb1a/1b;Abcg2-/- Cyp3a-/- 0 500 1000 1500 Brainconcentration (ng/g) Wild-type Abcg2-/- Abcb1a/1b-/- Abcb1a/1b;Abcg2-/- Cyp3a-/- 0 200 400 600 800 1.9-fold 25.5-fold ** 2.2-fold *** 1-fold * Liver toplasma ratio Wild-type Abcg2-/- Abcb1a/1b-/- Abcb1a/1b;Abcg2-/- Cyp3a-/- 0 20 40 60 80 100 * Brain toplasma ratio Wild-type Abcg2-/- Abcb1a/1b-/- Abcb1a/1b;Abcg2-/- Cyp3a-/- 0 20 40 60 13.5-fold *** 1.3-fold 1.4-fold 0.9-fold Liver accumulation (h -1 ) Wild-type Abcg2-/- Abcb1a/1b-/- Abcb1a/1b;Abcg2-/- Cyp3a-/- 0.0 0.1 0.2 0.3 0.4 0.5 Wild-type Abcg2-/- Abcb1a/1b-/- Abcb1a/1b;Abcg2-/- Cyp3a-/- 0.0 0.1 0.2 0.3 Brainaccumulation ( h -1 ) * *** 1.9-fold 24-fold 2.2-fold ** 0.7-fold A B C D E F 24 hours after oral administration Figure 3 - Brain and liver concentration ( A, D ), tissue-to-plasma ratio ( B, E ) and relative tissue accumulation ( C, F ) of ponatinib in female WT, Abcg2 -/- , Abcb1a/1b -/- and Abcg2;Abcb1a/1b -/- mice 24 h after oral administration of 10 mg/kg ponatinib. *, P < 0.05; **, P< 0.01; ***, P < 0.001 compared to WT mice. Data are given as mean ± SD. n = 4-5 mice per group.